TWI434955B - Method for chemical mechanical planarization of a tungsten-containing substrate - Google Patents

Description

Chemical mechanical planarization method for tungsten-containing substrate Cross-reference to related applications

The benefit of the prior U.S. Provisional Patent Application Serial No. 61/304,574, filed on Feb. 15, 2010, is hereby incorporated by reference in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety.

The present invention relates generally to chemical mechanical planarization (CMP) of tungsten-containing substrates on semiconductor wafers and slurry compositions therefor. In particular, the present invention is useful for tungsten CMP where low disk/plug recesses and low array intrusion on a planarized substrate are desired and/or desired.

Chemical mechanical planarization (Chemical Mechanical Polishing, CMP) for planarization of semiconductor substrates is now well known to those skilled in the art and is described in the publications of numerous patents and publications. Introductory references for CMP are as follows: in Handbook of Semiconductor Manufacturing Technology, Chapter 15, pages 415 to 460, by "Chemical-Mechanical Polish" by GB Shinn et al., edited by Y. Nishi and R. Doering , Marcel Dekker, New York City (2000).

In a typical CMP process, a substrate (eg, a wafer) is brought into contact with a rotating polishing pad that is adhered to a platen. A CMP slurry, often a mixture of abrasive and chemically reactive, is supplied to the mat during the CMP treatment of the substrate. During the CMP process, the mat (fixed to the platen) and the substrate are rotated while the wafer carrying system or polishing head applies pressure to the substrate (under downward force). Due to the rotational motion of the mat in parallel with the substrate, the paste achieves the planarization (polishing) by chemically and mechanically interacting with the planarized substrate film. The polishing is continued in this manner until the desired film on the substrate is removed to achieve the common purpose of effectively planarizing the substrate. Typically the metal CMP slurry contains an abrasive material suspended in an oxidizing aqueous medium, such as cerium oxide or aluminum oxide.

A large amount of material is used in the manufacture of integrated circuits such as semiconductor wafers. These materials are generally classified into three types - dielectric materials, adhesion and/or barrier layers and conductive layers. Uses of a variety of different substrates, such as dielectric materials such as TEOS, PETEOS, and low-k dielectric materials; barrier/adhesive layers such as tantalum, titanium, tantalum nitride, and titanium nitride; and conductive layers such as copper, aluminum, Tungsten and precious metals are well known in this industry.

The integrated circuits are interconnected by the application of well known multilayer interconnects. The interconnect structure typically has a metallized first layer, an interconnect layer, a metallized second layer, and a typically metallized third and subsequent layer. The tantalum substrate or different metallization layers in the well are electrically separated by an interlayer dielectric material such as ceria and sometimes a low-k material. Electrical connections between different interconnect layers are accomplished through metallized vias and particularly tungsten vias. U.S. Patent No. 4,789,648 describes a method for preparing multiple metallization layers and metallized vias in an insulating film. In a similar manner, metal contacts are used to form an electrical connection between the interconnect layer and the components formed in the well. The metal vias and contacts are typically filled with tungsten and a metal layer, such as a tungsten metal layer, is typically adhered to the dielectric material using an adhesion layer such as titanium nitride (TiN) and/or titanium.

In a semiconductor fabrication process, metallized vias or contacts are formed by blanket tungsten deposition followed by a CMP step. In a typical method, vias are etched through the interlayer dielectric (ILD) to interconnect lines or semiconductor substrates. Next, a thin adhesion layer such as titanium nitride and/or titanium is formed substantially on the ILD and introduced into the etched via. Next, a tungsten film is deposited on the adhesion layer and in the via hole. This deposition is continued until the via is filled with tungsten. Finally, excess tungsten is removed by chemical mechanical polishing (CMP) to form metal vias.

The ratio of the removal rate of metal (eg, tungsten) to the removal rate of the dielectric substrate is referred to as the removal of the metal relative to the dielectric during CMP processing of the substrate comprising the metal and dielectric material. "Selective." When a CMP slurry having a metal having a high selectivity with respect to a dielectric is used, the metal layers are easily over-polished in the metallized region to cause a dishing or "disc" effect. This feature distortion is unacceptable due to lithographic etching and other constraints in semiconductor fabrication.

Another feature that does not apply to semiconductor manufacturing is the distortion called "erosion." Erosion is the difference in morphology between a dielectric field and a dense array of metal vias or trenches. In CMP, the material in the dense array can be removed or eroded at a faster rate than the surrounding dielectric field. This results in a topographical difference between the dielectric field and the dense metal (e.g., copper or tungsten) array.

As industry benchmarks become more and more feature-oriented, there is a continuing need for CMP slurries that can provide excellent planarization of IC wafer nanostructures. Specifically, with regard to the 45 nm technology node and smaller feature sizes, the slurry product must be given a low removal rate selectivity between the metal and the dielectric to reduce erosion while maintaining adequate removal rates and Low defect amount. Furthermore, in the competitive market for CMP consumables, low cost of ownership (CoO), specifically through the concentration of CMP slurry research, quickly became an industry benchmark.

The typically used CMP slurry has two functions, a chemical composition and a mechanical composition. An important consideration for slurry selection is the "passive etch rate." The passivation etch rate is the rate at which the metal (e.g., copper) is dissolved by the chemical component alone, and should be significantly lower than the rate of removal when the chemical composition and the mechanical component are involved. The large passivation etch rate results in dishing of the metal trenches and vias, and therefore, preferably, the passivation etch rate is less than 10 nm per minute.

These are the three common types of layers that can be polished. The first layer is an interlayer dielectric (ILD) such as hafnium oxide and tantalum nitride. The second layer is a metal layer, such as tungsten, copper, aluminum, etc., which is used to join the active components. This case proposes polishing the metal layer, in particular tungsten. The layer of the third type is an adhesion/barrier layer such as titanium nitride.

In the case of metal CMP, this chemistry is generally considered to take one of two forms. In the first mechanism, the chemical in the solution reacts with the metal layer to continue to form an oxide layer on the surface of the metal. This generally requires the addition of an oxidizing agent such as hydrogen peroxide, ferric nitrate or the like to the solution. The mechanical grinding of the particles continuously and simultaneously removes the oxide layer formed on the metal layer. From the standpoint of the removal rate and the quality of the polished surface, the equalization of these two methods will yield the most appropriate results.

In the second mechanism, no protective oxide layer is formed. Rather, the constituents of the solution chemically attack and dissolve the metal, while the mechanical action is mostly a method of mechanically increasing the rate of dissolution by, for example, continuously exposing more surface area to Under the chemical attack, the local temperature (which increases the dissolution rate) is increased by the friction between the particles and the metal, and the diffusion of the reactants and products to and from the surface is enhanced by mixing and reducing the thickness of the boundary layer. phenomenon.

The slurry composition is one of the important factors in the CMP step. Depending on the choice of oxidizing agent, abrasive, and other useful additives, the polishing slurry can be tailored to provide effective polishing of the metal layer at the desired polishing rate while causing defects and defects in the surface of the tungsten-containing via. Corrosion and erosion are minimized. Furthermore, the polishing slurry can be used to provide controlled polishing selectivity to other film materials used in modern integrated circuit technology, such as titanium and titanium nitride.

In particular, there is a clear need for a tungsten CMP process and slurry that provides low dishing and reduced plugging effects in view of the fact that the semiconductor industry continues to move toward smaller and smaller feature sizes. The present invention provides a solution to this significant need.

In one embodiment, the invention is a method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface of the substrate with a) an abrasive, and b) a liquid component, the liquid group a fraction comprising water; an acid sufficient to provide a pH of from 2 to 5, such as between 2.5 and 4.5, preferably a mineral acid; a per-oxidizer; a copper between 1 ppm and 100 ppm Or an iron compound which reacts with the oversized oxidant at an elevated temperature to synergistically increase the tungsten removal rate; and between 0.1 and 10 ppm of poly(alkyleneimine), for example comprising or substantially An oligomer composed of ethyleneimine, acrylimine or both, for example, a molecular weight of from about 2,000 to more than 1,000,000, more usually between 10,000 and 140,000.

In one embodiment, the invention is a method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface of the substrate with a) an abrasive, and b) a liquid component, the liquid group a fraction comprising water; an acid sufficient to provide a pH of from 2 to 5, such as between 2.5 and 4.5, preferably a mineral acid; a per-type oxidizing agent; an iron compound between 1 ppm and 100 ppm, which is increased Reacting with the over-type oxidant at a temperature to synergistically increase the tungsten removal rate; and between 0.1 and 10 ppm of polyethyleneimine, wherein in a preferred embodiment the liquid component is substantially free of carboxylic acids And the polishing action removes tungsten above 2000 angstroms per minute ("Angstroms per minute") under a 3 psi downward force. If iron is bonded to the abrasive surface, all of the iron in the slurry is typically from 5 ppm to 20 ppm based on the total weight of the slurry.

In another embodiment, the invention is a method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface having tungsten thereon with a) an abrasive suspended in a liquid to form a slurry The slurry comprises between 0.3 and 1% by weight, for example between 0.4 and 0.7% by weight, of the abrasive comprising water, an acid sufficient to provide a pH of 2 to 5, a peroxide oxidizing agent And a polyethyleneimine between 0.1 and 10 ppm, the liquid being substantially free of fluorochemicals, wherein the polishing removes tungsten above 2000 angstroms per minute.

In another embodiment, the invention is a method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: contacting a surface having tungsten thereon with a) an abrasive comprising cerium oxide, and b) moving the liquid component In contact with the ground, the liquid component comprises water; an acid sufficient to provide a pH of 2 to 5; a peroxide oxidizing agent; and a polyethyleneimine between 0.1 and 10 ppm, and a ratio between 0.01 and 4 ppm. Ethylene pentamine, wherein the polishing removes tungsten above 2000 angstroms per minute.

In another embodiment, the invention is a method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface of the substrate with a) an abrasive, and b) a liquid component, the liquid The component comprises water; an acid sufficient to provide a pH of 2 to 5; a peroxide oxidizing agent; an iron compound between 1 ppm and 60 ppm which reacts with the oversized oxidant at elevated temperature to cause free radical formation to increase tungsten The removal rate; and between 0.1 and 10 ppm of polyethyleneimine, and wherein the polishing removes tungsten above 2000 angstroms per minute.

In another embodiment, the invention is a method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface of the substrate with a slurry comprising: between 30 and 90 The average diameter between nm and the iron bonded to the surface of the first cerium oxide abrasive, which can increase the temperature from the over-type oxidant to generate free radicals to increase the tungsten removal rate; between 120 and 240 nm An average diameter of the second cerium oxide abrasive; water; an acid sufficient to provide a pH of 2 to 5; a peroxide oxidizing agent; and a polyethyleneimine between 0.1 and 10 ppm, and wherein the polishing removal is high Tungsten at 2000 angstroms per minute.

With regard to the various specific embodiments described in the first five paragraphs, the following improvements may be beneficially employed, either individually or in combination. In each of the above specific embodiments, the phrase polyethyleneimine means a polymer and oligomer comprising or consisting essentially of ethyleneimine, acrylimine or both, for example from about 2,000 to over 1,000,000, More often, the molecular weight is between 10,000 and 140,000.

In each of the above specific embodiments, the tungsten removal rate is advantageously greater than 2000 angstroms per minute, but is preferably greater than 3000 angstroms per minute, and most preferably greater than 4000 angstroms per minute. In each of the above specific embodiments, although it is possible to polish the dielectric material if exposed to the slurry, the preferred slurry using this embodiment will result in less than 500 angstroms per minute at 3 psi, for example. A dielectric layer polishing rate of less than 400 angstroms per minute at 3 psi, preferably less than 100 angstroms per minute at 3 psi. In each of the above five specific embodiments, although it is possible to polish a variety of other materials if exposed to the slurry, the preferred slurry using this embodiment will result in less than 500 angstroms per minute at 3 psi. For example, a polysilicon polishing rate of less than 400 angstroms per minute at 3 psi, preferably less than 200 angstroms per minute at 3 psi. The polyethyleneimine is preferably present in an amount of less than 6 ppm, for example less than 5 ppm, for example between 1 and 4 ppm. Although a little additional static etch corrosion protection is used, the use of larger amounts of polyethyleneimine results in a reduced tungsten removal rate. In each of the above five specific embodiments, the amount of polyethyleneimine is preferably between 0.1 and 4 ppm, for example between 0.3 and 3 ppm. The phrase "ppm" means the parts per million parts by weight of the slurry (liquid plus abrasive) or the liquid component if there is no abrasive suspended in the liquid. In each of the above five specific embodiments, an exemplary pH is from 2.5 to 4.5, more preferably from 2.5 to 4, for example from 2.5 to 3.5. At low pH, a chelating agent is not necessarily required. Chelating agents reduce the properties of the slurry during long-term storage and make cleaning and handling/recycling of the water difficult. In one of the above five specific embodiments, the presence of carbonaceous compounds and especially polyetheramines and carboxylic acids in the liquid (other than less than 10 ppm or less of polyethyleneimine) does not like And in the preferred embodiment of the polishing composition, it does not contain polyetheramines and/or carboxylic acids, or contains less than 50 ppm, 20 ppm, 10 ppm or 5 ppm of these carbon-containing compounds. In one aspect of each of the above specific embodiments, the liquid portion of the polishing composition additionally comprises from about 0.1 to about 5 ppm of tetraethyleneamine. In one aspect of each of the above five specific embodiments, the polishing composition is free of fluorine-containing compounds, particularly fluorine-containing compounds that attack dielectric materials, and in a preferred embodiment the polishing composition is free of fluorine-containing compounds. A compound, or a fluorochemical containing less than 50 ppm, 20 ppm, 10 ppm, or 5 ppm. More preferably, it is a fluorine-containing compound having no or less than 1 ppm. In one of the above five specific embodiments, the oversized oxidant is necessary, and preferred embodiments include one or more iron or copper compounds, typically between 5 ppm and 60 ppm. The amount is preferably bonded to at least one type of cerium oxide abrasive surface in an amount sufficient to cause free radicals from the oversized oxidant at elevated temperatures to synergistically increase the tungsten removal rate. In one of the above five specific embodiments, the polishing composition is free of chelating compounds, such as polycarboxylic acids, and in a preferred embodiment the polishing composition is free of chelating compounds, or Contains less than 50 ppm, 20 ppm, 10 ppm or 5 ppm of chelating compound. More preferably, it is a chelate compound having no or less than 1 ppm. Surprisingly, no chelating compounds (except for trace amounts of polyimines, such as polyethyleneimine) in the slurry provide high tungsten removal rates and low contamination. In one of the above five specific embodiments, the polishing composition is free of polyamines or contains less than 50 ppm, 20 ppm, 10 ppm, 5 ppm or 1 ppm of polyamine. In one of the above five specific embodiments, the polishing composition contains no reducing agent such as formic acid, oxalic acid or formaldehyde, or contains less than 50 ppm, 20 ppm, 10 ppm or 5 ppm of reducing agent, such as formic acid, Oxalic acid or formaldehyde. Advantageously, in each of the above five specific embodiments, the slurry contains a bimodal distribution of abrasive size, and is preferably a trimodal distribution of abrasive size. The particle size is provided from the standpoint of average diameter, with most of the particle samples of a particular size typically having particles ranging from about 20% to 30% of the average particle size of the sample. The polishing action generates heat, and the reactivity of the iron-activated over-type oxidant such as hydrogen peroxide which is activated by a small amount of iron compound to uniformly form a radical by hydrogen peroxide has a very high heat sensitivity. The heat generated by the polishing and the heat removed by conduction and other means vary with respect to the position of the wafer and the polishing pad, and as a result the temperature of the slurry against the wafer being polished may be relative to the crystal The position of the circle changes. The reactivity of an iron-activated over-type oxidant such as hydrogen peroxide which is activated by a small amount of iron compound to uniformly form a radical by hydrogen peroxide has a very high heat sensitivity. This can result in an excessively high removal rate in the middle of the wafer. Using a small (average particle size between 30 nm and 90 nm, for example between 40 nm and 70 nm) the thermal effect of iron coated particles with a oxidizing agent can be used A substantial portion of the larger particles, for example, an uncoated iron cerium oxide abrasive having a smaller average particle size of about 3 to 5 times the size of the iron coated particles, is included for substantial remedy. If a part of the iron is distributed on other abrasives, it is not necessary to iron coat the smaller particles. The amount of large abrasive is typically between 0.2 and 2 times, for example, between 0.5 and 1.5 times the weight percent of the small diameter abrasive. In addition, the presence of medium-sized abrasives, for example between 1.5 and 2.5 times the diameter of the smaller iron-coated particles, substantially increases the tungsten removal rate without increasing or even reducing dishing. . The amount of medium abrasive is typically between 0.2 and 6 times, for example, between 0.5 and 5 times, preferably 0.6 to 1.5 times the weight percent of the small diameter abrasive. Other medium abrasives can be included but are not particularly beneficial. Since the benefits of a variety of different improvements each can result in superior performance, the various improvements in this paragraph can be applied to any of the five main embodiments of the present invention and can be further combined with other improvements.

The present invention relates to a method of utilizing a related slurry for chemical mechanical planarization of a tungsten-containing substrate. The minimization or prevention of dishing/erosion and features of the plunger on the semiconductor substrate and the selectivity of the selectivity during CMP processing are becoming more and more important as the semiconductor industry tends to become more and more in the manufacture of integrated circuits. The smaller the feature size.

The slurry utilized in accordance with the method of the present invention is used to polish tungsten and will be described next. The slurry comprises polyethyleneimine, an oxidizing agent (eg, a peroxide oxidizing agent), a liquid component comprising water, an acid, and an abrasive. Optionally, the slurry may contain an iron compound to initiate free radical formation of the overtype oxidant to increase the tungsten removal rate.

The polyethyleneimine (PEI) of the slurry can be branched or linear. Preferred polyethyleneimines are branched polyethyleneimines. At least half of the polyethyleneimine is preferably branched. Linear polyethyleneimine contains all secondary amines, which are quite different from branched PEIs containing primary, secondary and tertiary amine groups. The branched polyethyleneimine can be represented by the formula (-NHCH ₂ CH ₂ -) _x [-N(CH ₂ CH ₂ NH ₂ )CH ₂ CH ₂ -] _y , wherein x can be from 2 to >40; y may be from 2 to >40, preferably x and y are each independently from 11 to 40, or that x and y are each independently from 6 to 10, and x and y may independently be from 2 to 5, Shown in the following:

The PEI reduces static etching or erosion to substantially none, that is, below 20 angstroms per minute. A problem with aggressive tungsten pastes is that their chemistry can attack tungsten during idle periods, for example, when not polished, that is, the motion of the abrasive is insufficient to remove the oxide coating formed by the oxidation system. In the absence of PEI, static etching of the iron-catalyzed peroxide system can be as high as 200 to 300 angstroms per minute. For iron-catalyzed systems, as little as 0.1 ppm of PEI reduces static etch, and as little as 1 or 2 ppm PEI reduces static etch to 25 Å/min. Surprisingly, a very small amount of PEI has efficacy in the slurry. The amount of PEI in the slurry is from 0.1 ppm to 10 ppm and preferably from 0.5 ppm to less than 5 ppm, for example from 1 ppm to 3 ppm. One problem with this type of corrosion inhibitor is that the corrosion inhibitor causes foaming (a serious manufacturing problem) when the amount is as small as 10 ppm or 20 ppm depending on the weight of the mole and other factors. When the slurry used in the present invention has a preferred concentration, no foaming occurs.

Suitable oxidizing agents include, by way of example, one or more per-compounds comprising at least one peroxy group (-OO-). Suitable per compounds include, for example, peroxides (e.g., hydrogen peroxide and urea hydrogen peroxide), persulfates (e.g., monopersulfates and dipersulfates), percarbonates. Peroxyacids (eg, peracetic acid, perbenzoic acid, m-chloroperbenzoic acid, salts thereof), perchlorates, perbromates, periodate salts and their acids, and mixtures thereof Class) and its mixtures, etc. Preferred oxidizing agents include hydrogen peroxide, urea hydrogen peroxide, sodium or potassium peroxide, benzammonium peroxide, dibutyl peroxide, peracetic acid, monopersulfuric acid, dipersulfuric acid, iodic acid and salts thereof. Classes, and mixtures thereof. Hydrogen peroxide (H ₂ O ₂ ) or peracetic acid is a preferred oxidizing agent. In one embodiment, the oxidizing agent is hydrogen peroxide. Strong acid oxidants, such as nitric acid, can also be used. The over-type oxidizing agent or strong acid oxidizing agent is typically present in an amount between about 0.1% and 10%, for example between 0.5% and 6%, and advantageously between 1% and 5% by weight. between. When used, the preferred concentration of H ₂ O ₂ is from about 0.5% to about 4%, for example between 1% and about 3%.

In one embodiment, the oxidizing agent is capable of forming free radicals (eg, hydrogen peroxide) in the presence of iron or copper present in the polishing composition, which results in an increased rate of tungsten removal.

Abrasives suitable for use in the present invention include, but are not limited to, alumina, cerium oxide, gallium oxide, cerium oxide, titanium oxide, zirconium oxide, and mixtures thereof. In one embodiment, the abrasive is cerium oxide (colloidal cerium oxide or fuming cerium oxide). In one embodiment, the abrasive is colloidal cerium oxide. In a preferred embodiment, at least 0.1% by weight of the abrasive is present compared to the total weight of the abrasive and the liquid. The amount of the abrasive in the slurry is not limited but is preferably less than 5%, more preferably about 3 weight percent or less, and in some embodiments less than the total weight of the abrasive and the liquid. 1 weight percent.

In one embodiment, the metal modified abrasive, for example, iron coated cerium oxide, is present as a component. This component is used to initiate free radical formation of the over-type oxidant to increase the removal rate of tungsten (or other metals).

In various embodiments, the slurry can comprise two or more different abrasives having different sizes. In these embodiments, the total amount of the abrasive is preferably less than 1 weight percent.

The choice of acid is not limited, provided that the strength of the acid is sufficient to supply a pH of 2 to 5 of the slurry. Examples of suitable acids are mineral acids such as nitric acid, phosphoric acid or sulfuric acid.

The solvent to be supplied as a main portion of the liquid component may be water or a mixture of water and other water-miscible liquids. Examples of other liquids are alcohols such as methanol and ethanol. Advantageously the solvent is water.

The slurry composition used in the process of the invention is acidic and has a pH between 2 and 5. Preferably, the pH is between 2.5 and 4.5, and more preferably, the pH is between 2.5 and 4, for example 2.5 to 3.5.

Carbonaceous compounds (other than a few ppm of polyethyleneimine) and especially carboxylic acids are not preferred in the slurry composition. In a preferred embodiment, the polishing composition is free of carboxylic acids or contains less than 50 ppm, 20 ppm, 10 ppm or 5 ppm of carbonaceous compounds, including the polyethyleneimine. Another unsuitable carbonaceous compound is a polyetheramine. In a preferred embodiment, the composition is free of polyetheramine or contains less than 50 ppm, 20 ppm, 10 ppm or 5 ppm of carbonaceous compounds, including the polyetheramine. Carbon-containing chemicals increase the disposal problem because they cannot be easily removed.

The presence of a fluorine compound in the slurry is not suitable because it attacks the dielectric. In a preferred embodiment, the polishing composition is free of fluorochemicals or contains less than 50 ppm, 20 ppm, 10 ppm or 5 ppm of fluorochemical.

Advantageously, no reducing agent such as formic acid, oxalic acid or formaldehyde is present in the slurry.

Some CMP patents describe the use of polyamine as a component in CMP slurries. It is emphasized here that polyamine is not a polyethyleneimine.

method

The related methods of the present invention are necessarily accompanied by the use of the aforementioned composition for chemical mechanical planarization of a substrate comprising tungsten and a dielectric material (as previously disclosed). In this method, the substrate (e.g., wafer) is placed face down on a polishing pad that is firmly adhered to the rotary platen of the CMP polisher. In this manner, the substrate to be polished and planarized is brought into direct contact with the polishing pad. The substrate is held in position using a wafer carrying system or polishing head and a downward pressure is applied to the back side of the substrate during the CMP process while the platen is rotated with the substrate. The composition (slurry) is applied (usually continuously) on the mat during the CMP process to effect the removal of the material to planarize the substrate.

In the compositions of the present invention and related methods, the rate of tungsten removal is maintained at at least 2000 angstroms per minute by chemical mechanical polishing when polishing at a downward force of 3 psi. A higher removal rate will be achieved when a downward force greater than 3 psi is used.

As indicated above, a specific embodiment of the invention is a composition for chemical mechanical polishing of a tungsten-containing substrate. In a specific embodiment, the substrate also has at least one feature comprising a dielectric material on the surface, at least close to the polishing inference. In a specific embodiment, the dielectric material is yttrium oxide.

With respect to the method of the present invention and the use of related slurries, the polysilicon and dielectric layer polishing rates are preferably less than 500 angstroms per minute, typically less than 250 angstroms per minute, and these polishing rates are preferably less than 100 per minute. Ai. These pastes have a tungsten to dielectric selectivity between 8 and 40, typically between 12 and 24. When used in a plurality of different embodiments of the present invention, the presence of 1 to 3 ppm of PEI can substantially reduce array erosion (about 10% to 30%) compared to an equivalent slurry without PEI. ), plunger depression (about 10%) and average dish (about 10% to 15%).

The invention will be further confirmed by the following examples.

Example General

All percentages are by weight unless otherwise indicated.

CMP methodology

In the examples shown below, CMP experiments were carried out using the procedures and experimental conditions provided below.

vocabulary Component

Iron coated cerium oxide: colloidal cerium oxide at a solids content of 2.5% by weight, having a particle size of about 45 nanometers (nm); the cerium oxide particles are coated with iron to such an extent that iron atoms Bonded to about 25% of the allowable binding sites on the cerium oxide particles.

Medium-sized colloidal cerium oxide: colloidal cerium oxide particles (NexSil 50ZK-DI) supplied by Nyacol, Mass., with an average particle size of about 80 nm.

Large colloidal cerium oxide: colloidal cerium oxide particles having an average particle size of about 180 nm.

Ethyleneimine oligomer mixture: polyethyleneimine with a small amount of tetraamethyleneamine.

(from the MSDS of this product >=5% and <=20%)

Supplied by Sigma-Aldrich, Louis Street, Missouri

PEI: Polyethyleneimine (Aldrich, Milwaukee, Wisconsin)

TEOS: tetraethyl orthosilicate

Polishing pad: polishing pad Politex And the IC1000 was used during the CMP period and was supplied by DOW Ltd. (formerly supplied by Rodel (Rohm and Haas), which is now part of DOW Ltd.).

parameter

General

: ang-length unit

BP: back pressure, in psi

CMP: chemical mechanical planarization = chemical mechanical polishing

CS: Vehicle speed

DF: downward force: pressure applied during CMP, in psi

Min: minute

Ml: ml

mV: millivolt

Psi: pounds per square foot

PS: Platen rotation speed of polishing machine, unit rpm (revolutions per minute)

SF: slurry flow rate, ml/min

Weight%: (% of the listed ingredients)

W: TEOS selectivity: (W removal rate) / (TEOS removal rate)

Removal rate

Tungsten removal rate: The rate of tungsten removal measured at a specified downward pressure. The CMP tool has a downward pressure of 3 psi in the following examples.

CMP methodology

In the examples shown below, the CMP experiment was carried out using the procedures and experimental conditions provided below.

Metrology

The tungsten film was measured using ResMap CDE, Model 168, manufactured by Creative Design Engineering Co., Ltd., No. 20565, Dr. O'Reilly, Curtin, California, 95014. This ResMap machine is a four-point probe type surface resistance tool. The tungsten film was scanned for a 49-point diameter at a distance of 5 mm from the edge.

CMP machine

The CMP machine used was Mirra, manufactured by Applied Materials, 3050 Brads Avenue, Santa Clak, California. The IC1000 is used on the platen 1, and a groove is stacked on the suba IV mat (previously supplied by Rodel) supplied by DOW Co., Ltd., No. 451 Baylord Road, Newark, USA, for use in Research on blank wafers and patterned wafers. A Politex mat was used on the platen 3, supplied by DOW Co., Ltd., for polishing on the platen 1 for TEOS defective wafers.

The IC1000 mat was broken by adjusting the mat for 18 minutes with a downward force of 7 lbs. The Politex mat was damaged by polishing 20 TEOS imitation wafers with deionized water. In order to make the tool setting and mat test run, use the Microplanar supplied by DuPont Air Products NanoMaterials LLC for the reference conditions. CMP3850 polished tungsten display and two TEOS monitors.

Wafer

Polishing experiments were performed using CVD deposited tungsten wafers. These blank wafers were purchased from Silicon Valley Microelectronics, 2985 Kafur Road, Santa Cruz, CA 95051. The film thickness specifications are summarized as follows: W: 8,000 CVD tungsten; 240 TiN; 5000 TEOS is on the board.

Polishing experiment: In a blank wafer study, a tungsten blank wafer was polished under reference conditions. The equipment reference conditions were: table speed: 120 rpm; head speed: 123 rpm; membrane pressure: 3.0 psi; tube pressure: 6.0 psi; retaining ring pressure: 6.5 psi; slurry flow rate: 120 ml/min.

The slurry was applied to a patterned wafer (SKW5-3 supplied by SWK Associates, 2920 Scottrade Avenue, Santa Cruz, CA, USA) in a polishing experiment. These wafers were measured by a Veeco VX300 profiler/AFM instrument. The 100x100 micron line structure was used for dishing measurements and the 1x1 micron array was used for erosion measurements. Wafers are measured at the center, middle, and edge die locations.

Corrosion inhibitor containing PEI

The corrosion inhibitor used in the slurry of Examples 1 to 18 was an ethyleneimine, an oligomer mixture supplied by Sigma-Aldrich. This product contains polyethyleneimine (PEI) as the main component and tetraethyleneamine (TEPA) as a secondary component. The amount of TEPA described in the Material Safety Data Sheet is greater than or equal to 5% and less than or equal to 20%.

The corrosion inhibitor used in the slurry of Example 19 was polyethyleneimine (PEI) as a separate component (with the exception of a few impurities, if any). This product is supplied by Aldrich, Milwaukee, Wisconsin.

General procedure for making stock

All slurries are manufactured using the following general procedures:

a. In a 5-liter beaker, 473.36 grams of iron coated cerium oxide was added to 2610.12 grams of deionized water and allowed to stir with a magnetic stirrer for 2 minutes.

b. Under agitation, add 29.95 grams of Nyacol NexSil 50ZK-DI.

c. After 2 minutes of stirring, 17.73 grams of large colloidal cerium oxide was added.

d. After 2 minutes of stirring, 7 grams of ethyleneimine oligomer solution was added.

e. After 2 minutes of stirring, 11.84 grams of dilute nitric acid was added to adjust the pH of the solution to a pH of 2.5.

f. Just prior to polishing, add 350 grams of 30% hydrogen peroxide.

(The specified amount listed is the amount in the slurry of Example 1)

Examples 1 to 4

The slurry was prepared as shown in Table 1 and the slurry was tested and the pH of the slurry was varied from 2.5 to 4.0. The data in Table 1 shows that although the pH of the slurry is increased from 2.5 to 4.0, the W/TEOS selectivity is also reduced due to the TEOS removal rate. And improve. Also in this pH range, tungsten removal shows a slight decrease due to the pH increase of the slurry. As shown in Table 1, when the pH of the disclosed tungsten paste was gradually increased from 籨2.5 to 4.0, the removal rate of tungsten and TEOS gradually decreased, and the percentage of removal rate of TEOS decreased was greater than the percentage of removal rate of tungsten. Therefore, the selectivity of W/TEOS will increase from 20 to 46 when the pH is changed from 2.5 to 4.0.

Examples 5 to 7

The slurry was made as shown in Table 2 and the slurry was tested and the hydrogen peroxide concentration was varied. Table 2 lists the effect of peroxide concentration on tungsten and TEOS removal rates and the selectivity of W/TEOS. When the hydrogen peroxide concentration is increased from 1% to 2%, then, up to 3%, the tungsten removal rate will increase by about 43% and 24%, respectively. The increase in hydrogen peroxide concentration has little effect on the removal rate of the TEOS film. An increase in tungsten removal rate at an increased hydrogen peroxide concentration and an almost constant TEOS removal rate result in an increase in W/TEOS selectivity. The W/TEOS selectivity is increased from 12 to 20 when the amount of hydrogen peroxide is increased from 1 to 3 weight percent.

Examples 8 to 13

The slurry was produced as shown in Table 3 and the slurry was tested and the amount of colloidal cerium oxide changed. This table shows the effect of increasing the concentration of this medium-sized colloidal cerium oxide on the removal rate of tungsten and TEOS. As shown in Examples 8 and 9, the removal rate of tungsten was increased from 3376 angstroms/minute to 4582 angstroms/minute by introduction and using a 0.15% medium-sized colloidal cerium oxide abrasive. This means that the removal rate of tungsten has an increase in removal rate of about 36%. Increasing the tungsten removal rate by more than 47% by increasing the cerium oxide abrasive component from 0; in the case where the medium-sized abrasive is increased from 0.15 to 3%, when using 1% medium-sized glue The removal rate of tungsten at the state of the cerium oxide abrasive reaches a maximum removal rate; see Example 11. When the concentration of the colloidal cerium oxide exceeds the range of 0.15 wt% to 3% by weight, the TEOS removal rate is increased, causing the W/TEOS selectivity to decrease steadily as the medium-sized colloidal abrasive cerium oxide increases. .

Examples 14 to 17

The slurry was prepared as shown in Table 4 and the slurry was tested and the amount of corrosion inhibitor (polyethyleneimine) was varied. As shown in Table 4, the corrosion inhibitor concentration was increased from 1 ppm to 2 ppm, and then increased to 3 ppm, reaching a 2 ppm corrosion inhibitor concentration with the effect of reducing the tungsten removal rate and slightly increasing the TEOS removal rate. , or slightly reduce the effect of TEOS removal rate when the concentration of the corrosion inhibitor is increased from 2 ppm to 3 ppm, therefore, the W:TEOS selectivity first decreases from 33 to 28, and then drops to 17, after which, The W:TEOS selectivity remains the same.

Example 18 and Comparative Example 1

This inventive example and comparative examples illustrate the improved performance of the slurry of the present invention over the standard slurry (Comparative Example 1) without the corrosion inhibitor containing PEI or the medium colloidal cerium oxide component. In addition to adjustability, this inventive CMP slurry composition provides minimal tungsten die dishing and erosion compared to the standard paste. The data in Table 5 shows a comparison of the dishing and erosion between the standard slurry and this original tungsten paste. Measure the dishing and erosion of the grains at the center, middle and edge of the SKW 5-3 pattern wafer. The dishing is recorded as the difference in step height between the metal and the dielectric measured in a line of 100 μm, expressed in angstroms; the erosion is recorded as the step between the 1×1 μm line array of metal and the dielectric surrounding those arrays. Height difference. As shown in Table 5, the polishing results using this original slurry showed an improved dishing performance of about 10 to 20% better than the standard slurry. The use of this original slurry also improves the plunger sag and the erosion performance is similar to standard sizing.

Example 19 and Comparative Example 1

This inventive example and comparative examples illustrate the improved performance of the slurry of the present invention over the standard slurry (Comparative Example 1) without the corrosion inhibitor containing PEI or the medium colloidal cerium oxide component. The data in Table 6 shows a comparison of the dishing, erosion, and tungsten plug depressions between the standard slurry and the inventive tungsten paste. In the tungsten CMP slurry of this inventive example 19, only the PEI was used as the corrosion inhibitor in the PEI-containing corrosion inhibitor; there was no TEPA. Measure the dishing and erosion of the grains at the center, middle and edge of the SKW 5-3 pattern wafer. The dishing is recorded as the difference in step height between the metal and the dielectric measured in a line of 100 μm, expressed in angstroms; the erosion is recorded as the step between the 1×1 μm line array of metal and the dielectric surrounding those arrays. Height difference. As shown in Table 6, the polishing results using the slurry of Example 19 showed improved tungsten plug dent results, i.e., the standard slurry and the slurry of Example 19 decreased from 115 angstroms to 77 angstroms.

Static etch rate measurement

The static etch rate is a measure of experimental data that provides information about the chemical activity of the CMP slurry. Typically, a higher static etch rate indicates a more aggressive chemical composition that results in faster etching of the surface of the associated metal film and is more likely to cause more metal corrosion defects. The wafers from which the tungsten blank wafer was cut were exposed to a standard tungsten paste (Comparative Example 1), the Example 18 slurry, and the Example 19 slurry formulation, respectively. Table 7 shows the standard tungsten paste as The static etch rate of the /divide unit was compared to the static etch rate obtained using the pastes of Examples 18 and 19. Table 8 shows the normalized data collected at room temperature, 40 ° C, and 60 ° C for 20, 5, and 2 minutes, respectively. Many manufacturers only describe static etching at room temperature, but polishing produces heat. During some production interruptions, the wafer may be exposed to static etching of the slurry at a polishing temperature, ie 40 to 60 °C. The static etch rate using most oxidants is problematic and is more pronounced at elevated temperatures using an iron-peroxide oxidant system, which has a particularly strong activity. The addition of the selected corrosion inhibitor at room temperature and elevated temperatures reduces the static etch rate by at least 84%. This temperature-increasing data indirectly indicates that the temperature reached by the friction during polishing has excellent corrosion protection.

The trend in the development of CMP slurry suppliers is to reduce the cost of consumables for their consumers through product concentrations. The realization of providing a concentrated slurry becomes a requirement of the CMP industry. However, the concentration must be chosen with great care to avoid compromising the stability and shelf life of the product. The slurry composition of Example 18 was concentrated to 5 times (5 times the point concentration used). Disc and erosion data were obtained using both fresh (0 day) and 50 day concentrated samples diluted to point concentration. The data obtained represents a slight (less than 10 percent) change in tungsten and TEOS removal rate when the concentrated slurry is diluted to a point concentration using a 5-fold concentrated Example 18 slurry aging for 50 days. After 50 days of aging, the dishing performance changes by 8 to 25%, and the erosion changes by 5 to 20%.

The 5-fold slurry of Example 19 was similarly tested. The slurry composition of this Example 19 was concentrated to 5 times and tested in the same manner as shown in the slurry of Example 18 above. The data obtained indicates that after aging of the 5-fold concentrated Example 19 slurry, the concentrated slurry was diluted to a point concentration to exhibit a slight increase in tungsten and TEOS removal rates. After 50 days of aging, the dishing has hardly changed to less than 15%.

Slurry performance varies with slurry aging. The aging procedure includes short-term aging (aging of the slurry prepared in the tank within 3 days of use) and long-term aging (aging of the slurry concentration during storage for a plurality of periods). It has long been known to supplement a slurry with one or more compounds (typically with the addition of an oxidizing agent) to counteract short-term aging effects. The present invention proposes a long-term aging effect.

Preferred slurries of the present invention comprise a first (smaller) size iron coated cerium oxide and a second (larger) size iron free cerium oxide. Most preferred is a specific embodiment that also includes a third intermediate size abrasive. Specific compounds, such as carboxylic acids, should be avoided as a result of the coating of iron and uncoated iron. In general, organic materials can also adversely affect aging, so all of the preferred organics (except oxidizing agents) are between 0.1 and 10 ppm. Therefore, it is inevitable that any organic corrosion inhibitor exists in an amount of several ppm or less. Polyethyleneimine, especially branched polyethyleneimine, is a preferred corrosion inhibitor.

We have found that even with the use of slurry concentrations that minimize organics, these organics exacerbate long-term aging effects, and slurry concentrations exhibit some effects on aging, especially with regard to dishing and absolute tungsten removal rates. Note that the slurry concentrate contains no oxidizing agent, and the slurry concentrate is added when the slurry concentrate is mixed with water and an oxidizing agent in a tank to form a polishing slurry. It is known to adjust the slurry by adding a plurality of different components. The invention herein is a method of mixing two different slurry concentrates (commonly referred to as primary slurry concentrates and secondary slurry concentrates), wherein the mixing ratio of the slurry concentrates depends on the concentration of the primary slurry concentrates. Long-term aging to standardize slurry performance by aging. The primary slurry concentrate and the secondary slurry concentrate can be distinguished by one or more of the following: the amount of the first small abrasive, the amount of the second larger abrasive, the amount of any third medium abrasive, The amount of corrosion inhibitor and the amount of the mineral acid (effect, pH obtained). In addition, the method is expected to adjust the amount of oxidant added based on the long-term aging of the primary slurry concentrate. The result of mixing the slurry concentrates is that the original slurry ages less than 1 week, for example, 26 weeks or more, the substrate removal rate, dishing, erosion, and defect properties are substantially uniform. .

Claims (20)

A method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface of the substrate with a) an abrasive, and b) a liquid component comprising water; sufficient to provide 2 to 5 Acid of pH; per-type oxidizer; an iron compound between 1 ppm and 100 ppm which causes free radical formation of the oversized oxidant to increase the tungsten removal rate; and between 0.1 and 10 Poly(alkyleneimine) between ppm, wherein the liquid component is substantially free of carboxylic acids, and wherein the polishing acts to remove tungsten above 2000 angstroms per minute at a 3 psi downward force. The method of claim 1, wherein the polyalkyleneimine is a polymer or oligomer of ethyleneimine. The method of claim 2, wherein the poly(alkyleneimine) has a molecular weight of from about 10,000 to more than 140,000. The method of claim 1, wherein the liquid component is substantially free of a fluorine-containing compound. The method of claim 2, wherein the liquid component is substantially free of a chelating compound. The method of claim 1, wherein the polyalkyleneimine is polyethyleneimine and is present in an amount of less than 6 ppm. The method of claim 2, wherein the polishing removes tungsten above 4000 angstroms per minute at a 3 psi downward force. The method of claim 2, wherein the substrate further comprises a dielectric material, wherein the polishing acts to remove a dielectric material below 400 angstroms per minute at a 3 psi downward force. The method of claim 2, wherein the substrate further comprises polysilicon, wherein the polishing removes polycrystalline germanium below 400 angstroms per minute at a 3 psi downward force. The method of claim 2, wherein the liquid component has a pH of from 2.5 to 4. The method of claim 2, wherein the abrasive comprises a first cerium oxide abrasive having an average diameter between 30 and 90 nm and the iron is bonded to the surface, the iron being capable of causing an over-type oxidant Free radical formation to increase the tungsten removal rate; and additionally comprising a second cerium oxide abrasive having an average diameter between 120 and 240 nm, wherein the weight percentage of the second abrasive is between the first The weight percentage of the agent is between 0.5 and 1.5 times. The method of claim 1, wherein the abrasive comprises cerium oxide in an amount of from 0.1% to 5% by weight, and the liquid component thereof, in comparison with the weight of the abrasive and the liquid component An iron compound containing water, 0.5% to 4% by weight of H ₂ O ₂ , between 1 ppm and 100 ppm, which causes radical formation of the oversized oxidant to increase tungsten removal rate, and between 0.1 With 6 ppm of polyethyleneimine. A method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface having tungsten thereon with a) an abrasive suspended in a liquid to form a slurry, the slurry comprising between 0.3 and 1 weight Between the % of the abrasive, the liquid comprises water, an acid sufficient to provide a pH of 2 to 5, a peroxide oxidizing agent, and a poly(alkyleneimine) between 0.1 and 10 ppm, the liquid being substantially absent Fluorine-containing compound wherein the polishing removes tungsten above 2000 angstroms per minute. The method of claim 13, wherein the polishing removes tungsten above 4000 angstroms per minute at a 3 psi downward force. The method of claim 13, wherein the polyalkyleneimine is a branched polyethyleneimine and is present in an amount of less than 6 ppm. The method of claim 13, wherein the substrate further comprises a dielectric material, wherein the polishing acts to remove a dielectric material below 400 angstroms per minute at a 3 psi downward force. The method of claim 13, wherein the substrate further comprises polycrystalline germanium, wherein the polishing acts to remove polycrystalline germanium below 400 angstroms per minute at a 3 psi downward force. The method of claim 13, wherein the liquid component has a pH of between 2.5 and 4. A method of chemical mechanical polishing of a tungsten-containing substrate, the method comprising: movably contacting a surface of the substrate with a) an abrasive, and b) a liquid component comprising water; sufficient to provide 2 to 5 Acid of pH; over-type oxidant; iron compound between 1 ppm and 60 ppm, which causes free radical formation of the over-type oxidant to increase tungsten removal rate; and between 0.1 and 10 ppm of poly( The alkylene imide), and the polishing action, removes tungsten above 2000 angstroms per minute at a 3 psi downward force. The method of claim 19, wherein the polyalkyleneimine comprises a polyethyleneimine in an amount between 1 and 4 ppm.